/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.log;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Factory for common {@link Log} delegates with Spring's logging conventions.
 *
 * <p>Mainly for internal use within the framework with Apache Commons Logging,
 * typically in the form of the {@code spring-jcl} bridge but also compatible
 * with other Commons Logging bridges.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @see org.apache.commons.logging.LogFactory
 * @since 5.1
 */
public final class LogDelegateFactory {

    private LogDelegateFactory() {
    }


    /**
     * Create a composite logger that delegates to a primary or falls back on a
     * secondary logger if logging for the primary logger is not enabled.
     * <p>This may be used for fallback logging from lower level packages that
     * logically should log together with some higher level package but the two
     * don't happen to share a suitable parent package (e.g. logging for the web
     * and lower level http and codec packages). For such cases the primary,
     * class-based logger can be wrapped with a shared fallback logger.
     *
     * @param primaryLogger   primary logger to try first
     * @param secondaryLogger secondary logger
     * @param tertiaryLoggers optionally, more fallback loggers
     * @return the resulting logger to use
     */
    public static Log getCompositeLog(Log primaryLogger, Log secondaryLogger, Log... tertiaryLoggers) {
        List<Log> loggers = new ArrayList<>(2 + tertiaryLoggers.length);
        loggers.add(primaryLogger);
        loggers.add(secondaryLogger);
        Collections.addAll(loggers, tertiaryLoggers);
        return new CompositeLog(loggers);
    }

    /**
     * Create a "hidden" logger whose name is intentionally prefixed with "_"
     * because its output is either too verbose or otherwise deemed as optional
     * or unnecessary to see at any log level by default under the normal package
     * based log hierarchy.
     *
     * @param clazz the class for which to create a logger
     * @return the created logger
     */
    public static Log getHiddenLog(Class<?> clazz) {
        return LogFactory.getLog("_" + clazz.getName());
    }

}
